Last week at internal Citrix Sales Engineer gathering, I was presenting stuff on Application Streaming, where I noted that Application Streaming cannot isolate 16-bit DOS applications.  Immediate response from the SEs, yes it does - I have it in production and it works.  … Things that make you go hum.  

I went home and tested it.  Answer: The SEs are completely right.

Why?  Our file system driver is kernel mode and “sees all”.  Same for the code that looks after processes coming and going.  There would be a problem with registry filtering and this would be a show stopper, except there is no registry for DOS apps.   So, I’ve been telling people for years that this is a product limitation, when it really isn’t.

Here’s a picture of Turbo Pascal, 1987 vintage, running under Citrix Application streaming.  Also note that I saved Hello.pas to the C:\Turbo directory, which shows up in per-user layer of isolation.